Situ plasma clean gas injection

ABSTRACT

A processing chamber with a showerhead and a chuck is cleaned using an injection of a gaseous cleaning agent through an aperture in the chuck into the processing chamber. Because the aperture is located directly under the showerhead, a portion of the gaseous cleaning agent passes through the face plate of the showerhead so that the inside of the showerhead may be cleaned as well. By applying a radio frequency power supply between the chuck and the showerhead, for example, by a coil located between the chuck and showerhead or applying the power directly to the chuck and the showerhead, the gaseous cleaning agent forms a plasma. Thus, the portion of the gaseous cleaning agent that passes through the face plate and into the showerhead is a plasma. The plasma is pumped out of the chamber through a pumping port so that the plasma continuously flows through the processing chamber.

Divisional of prior application Ser. No. 09/132,688 Filed Aug. 11, 1998,entitiled: In-situ Plasma Clean Injection. Now U.S. Pat. No. 6,277,235.

FIELD OF THE INVENTION

The present invention relates to chemical vapor deposition processingchambers and in particular to removing unwanted material from thesurfaces within a processing chamber.

BACKGROUND

Processing chambers, such as chemical vapor deposition (“CVD”) chambersare used to process work pieces, such as semiconductor wafers, lightcrystal diodes, flat panel displays, or other similar substrates. Duringprocessing, a substrate located within the processing chamber is exposedto reactive gases introduced into the chamber and the substrate hasmaterial deposited on it. During the processing of the substrate, theinside surfaces of the chamber itself are typically contaminated byresidual deposited material. Thus, in subsequent processing ofsubstrates within the contaminated chamber, unwanted particles may formwhen the reactive gases combine with the contamination on the chamber'ssurfaces and the particles may be deposited on the substrate. Thus,processing chambers must be periodically cleaned to avoid thecontamination of the substrates being processed.

Typically, processing chambers are in situ (automatically) cleaned usinga gaseous cleaning agent, activated with a plasma. In conventionalprocessing chambers, the cleaning agent gas is introduced into theprocessing chamber in the same manner as the reactive gases areintroduced during processing, e.g., through a gas inlet port, such as ashowerhead. Conventional processing chambers typically include a chuckthat supports the substrate and is positioned under the showerhead.During processing, the reactive gases flow out of the showerhead andover the substrate located on the chuck. The unused reactive gases arethen pumped out of the chamber through an exhaust port. Similarly,during a cleaning cycle, the gaseous cleaning agent flows out of theshowerhead and over the chuck. The gaseous cleaning agent is then pumpedout of the chamber through the exhaust port. Thus, the gaseous cleaningagent has approximately the same flow pattern as the reactive gas. Asthe gaseous cleaning agent is pumped through the chamber, the gaseouscleaning agent contacts the chamber's interior surfaces and reacts withthe contaminants on the chamber's surfaces to create a gaseousby-product, i.e., vapor, and particles of the contaminant. The vapor andparticles of the contaminant are then pumped out of the chamber alongwith the remaining gaseous cleaning agent through the exhaust port.

Where the cleaning process uses a plasma, radio frequency (RF) power isprovided within the processing chamber, forming a plasma to ionize thecleaning agent gas to enhance chemical reaction with the contaminationon the chamber's interior surfaces. The RF power is typically appliedbetween the showerhead and the chuck. Thus, the gaseous cleaning agentdoes not form a plasma until the gas has flowed out of the showerheadand into the RF field.

Unfortunately, contamination of the chamber can occur not only on thewalls and chuck of the chamber, but also on the interior walls of theshowerhead. This is particularly true where a non-plasma type process isbeing used, such as a parylene process. There are many forms ofparylene, such as parylene C, parylene N, and parylene AF4, by way ofexample. Parylene AF4 is the form best suited and, thus, typically usedfor VLSI semiconductor devices. Parylene polymer is a dielectricmaterial that will deposit on surfaces below 50° C. During processing,parylene is often deposited on the interior walls of the showerhead.Other CVD processing chambers, such as tungsten, titanium nitride, orsimilar non-plasma processes, can also undergo undesirable deposition ofthe material within the showerhead.

Cleaning a parylene processing chamber, or other such processingchamber, with a plasma activated cleaning agent does not adequatelyclean the interior of the showerhead. Consequently, the interior of theshowerhead has to be replaced or periodically cleaned manually, therebyincreasing deposition tool downtime. Consequently, the overallthroughput of the deposition tool is decreased.

Thus, an in situ plasma clean is needed for processing chambers that canclean the interior surfaces of the chamber including the interior of theshowerhead.

SUMMARY

A processing chamber includes a showerhead and a chuck. The face plateof the showerhead facing the chuck has a pattern of small holes. Thechuck has a central aperture connected to a gaseous cleaning agentsupply. The gaseous cleaning agent, such as Oxygen, flows through thechuck aperture into the processing chamber. Because the chuck apertureis located below the showerhead, a portion of the gaseous cleaning agentflows through small holes in the showerhead face plate to the interiorof the showerhead. The gaseous cleaning agent circulates within theshowerhead and back out through the holes in the showerhead face plate.A pumping (exhaust) port located downstream of the chuck pumps thegaseous cleaning gas out of the processing chamber. A radio frequencypower supply is provided to the chuck and the showerhead, forming anelectromagnetic field (plasma) between the chuck and showerhead. Thegaseous cleaning agent is ionized as it passes through theelectromagnetic field. Thus, the portion of the gaseous cleaning agentthat flows into the showerhead via the face plate is in the form of anionized gas.

An in situ plasma clean is provided by pumping any remaining gas out ofthe processing chamber until the chamber is at a base pressure, e.g.,below 10 mTorr. The gaseous cleaning agent then flows into the chamberthrough the aperture in the chuck. The pumping port pumps the gaseouscleaning agent and other reactant gases out of the chamber to maintain aconstant pressure and a continuous supply of the gaseous cleaning agent.By applying the radio frequency power and forming a plasma, the gaseouscleaning agent passing through the plasma is ionized, which effectivelychemical reactant cleans the processing chamber, including inside theshowerhead. The gaseous cleaning agent supply is turned off and apurging gas flows into the processing chamber, e.g., from theshowerhead, while the pumping port continues to pump gas out of thechamber. The purging gas supply is shut off and the pumping port pumpsout the remaining gas until the chamber is again at its base pressure.Processing within the chamber can then be recommenced. Advantageously,the plasma clean is automatically performed without opening theprocesses chamber to atmosphere and with a minimal downtime.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying figures, where:

FIG. 1 is a schematic diagram of a processing chamber, including a gasinlet showerhead with face plate, a chuck with an aperture, and anannular pumping port;

FIG. 2 is a side view of a processing chamber used in accordance withone embodiment of the present invention;

FIGS. 3A, 3B, and 3C are side views of a Fluent model of a processingchamber showing the flow patterns in the chamber at 0.7 Torr, where thegaseous cleaning agent flows through the aperture at 10 sccm, 30 sccm,and 50 sccm, respectively;

FIGS. 4A, 4B, and 4C are side views of modeling of a processing chambershowing the flow patterns in the chamber at 1.0 Torr, where the gaseouscleaning agent flows through the aperture at 10 sccm, 30 sccm, and 50sccm, respectively; and

FIG. 5 is a side view of chamber showing the pressure distributionwithin the chamber at 1.0 Torr with the gaseous cleaning agent flowingat 50 sccm, as shown in FIG. 4C.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a processing chamber 100, including agas inlet showerhead 102 with face plate 104, a chuck 106, and anannular pumping port 110. Annular pumping port 110 is connected to avacuum pump 112 that is used to pump gas out of chamber 100. Showerhead102 is connected to a reactive gas source 114 via valve 116. Chuck 106includes at least one aperture 108 that is connected to a gas source 118by way of a valve 122. Aperture 108 is centrally located in the surfaceof chuck 106. Gas source 118 supplies a gas to the back side of asubstrate located on chuck 106 via aperture 108 during substrateprocessing. Aperture 108 is also connected to a cleaning gas source 120by way of a valve 123. During cleaning there is no substrate located onchuck 106, and thus the cleaning gas flows unimpeded into chamber 100.

Showerhead 102 and chuck 106 are also electrically connected to an RFpower source 124, such that chuck 106 and showerhead 102 act as an anodeand cathode, respectively. Chamber 100 may alternatively be connected toRF power source 124 by a coil located between chuck 106 and showerhead102. In addition, temperature control elements are connected to chamber100, including chuck 106, showerhead 102, and the walls of chamber 100.The temperature control elements are controlled by temperaturecontroller 126.

During normal processing operations, a substrate (not shown), such as asemiconductor wafer, is automatically loaded into chamber 100 by anautomatic transportation mechanism (not shown). The substrate is thenclamped to chuck 106 using an electrostatic charge, a mechanical clamp,a vacuum clamp, or gravity. The substrate is cooled, e.g., below 25° C.,by chuck 106, while the interior surfaces of chamber 100 are heated,e.g., above 50° C., by temperature controller 126. Gas, such as helium,is supplied to the back side of the substrate from gas source 118 andaperture 108, to improve the heat transfer from chuck 106 to thesubstrate and control deposition on substrate backside.

One or more reactive gases are supplied to the interior of chamber 100from reactive gas supply 114 and showerhead 102. The reactive gas flowsthrough small holes in face plate 104 and over the surface of thesubstrate. One deposition option uses RF power supplied by RF powersource 124 to chuck 106, while grounding showerhead 102. Typically, RFpower source generates 200 watts at a frequency of 13.56 MHz, whichproduces an electromagnetic field between showerhead 102 and chuck 106.The electromagnetic field forms a plasma of the reactive gas flowingthrough face plate 104 so that deposition may occur. For example, duringparylene deposition RF power source 124 is used to generate a plasma todeposit a parylene adhesion layer. Once the parylene adhesion layer isgenerated, the RF power is turned off, and the remaining parylenedeposition occurs. A second deposition option does not use RF power.Vacuum pump 112 is used to pump out the excess gas within chamber 100through annular pumping port 110 so that a constant pressure ismaintained within chamber 100.

As a result of the processing of the substrate, contaminants aredeposited on the interior surfaces of chamber 100. Moreover, duringcertain types of processing, such as deposition of parylene polymer,contaminants are deposited on the interior surfaces of showerhead 102.The interior surfaces of showerhead 102 typically show a higherdeposition rate than the walls of chamber 100 because the temperature ofshowerhead 102 is typically lower than the temperature of the walls.Periodically an in situ cleaning cycle is used to remove thecontaminates within chamber 100. The in situ cleaning cycle can be usedwhen it is determined necessary by inspection of the deposited substratefilm for contamination, or may be performed at regular intervals such asafter a predetermined thickness of film has been deposited, e.g., 10 μm(micrometers).

FIG. 2 is a side view of chamber 100 used in accordance with oneembodiment of the present invention. As shown in FIG. 2, chamber 100includes showerhead 102 with face plate 104, chuck 106 with aperture108, and annular pumping port 110. The walls of chamber 100, includingthe surfaces of showerhead 102 are manufactured out of aluminum, or anysimilarly rigid, non-corrosive material. One example of chamber 100 isthe parylene AF4 processing chamber model manufactured by NovellusSystems, Inc. located in San Jose, Calif. which includes aperture 108,and injects a cleaning gas through aperture 108.

Chuck 106 is a conventional electrostatic chuck for a 200 mm wafer,which uses an electric charge to clamp the wafer to the surface of chuck106. Fillers around the parameter of chuck 106 may be used when chamber100 is designed for expansion to 300 mm wafers. As discussed above, theaperture 108 in chuck 106 is used during processing to supply helium orother similar gas to the back side of the wafer to aid in heat transferand control substrate backside deposition. The use of chuck 106 tosupply a gas to control substrate backside deposition is described indetail in U.S. patent application Ser. No. 08/938,206, filed on Sep. 26,1997, having the same assignee and is incorporated herein by reference.Of course, chuck 106 is not limited to an electrostatic chuck or to achuck sized for only a 200 mm wafer. Other chuck sizes may be used aswell as other methods of holding the wafer on the surface of chuck 106may be used.

Showerhead 102 is likewise sized for a 200 mm wafer, but of course thesize of showerhead 102 may be altered to accommodate other size wafersif desired. Face plate 104 of showerhead 102 has a plurality ofuniformly spaced small diameter holes that permit the parylene monomergas to flow through face plate 104 during processing. Face plate 104, byway of an example, has approximately 8,407 uniformly distributed holes,each of which is 1.5 mm in diameter.

As shown in FIG. 2, chamber 100 has an internal length L₁₀₀ ofapproximately 350 mm, and an internal height H₁₀₀ of approximately 110mm. Face plate 104 and the top surface of chuck 106 have a diameter D₁₀₄of approximately 208 mm. Annular pumping port 110 has a diameter D₁₁₀ ofapproximately 98 mm, and the portion of showerhead 102 that extendsthrough annular pumping port 110 has a diameter D₁₀₂ of approximately 46mm. The distance L_(side) between an interior side wall of chamber 100and the largest diameter of showerhead 102 is approximately 62 mm. Thediameter D₁₀₈ of aperture 108 is 4 mm.

The height H₁₀₆ of chuck 106 is approximately 28 mm, while the distanceH₁₀₄ between the top surface of chuck 106 and the bottom surface of faceplate 104 is approximately 26 mm. The distance H₁₀₂ between the topsurface of face plate 104 and the interior surface of showerhead 102 isapproximately 36 mm. The distance H_(top) between the top surface ofshowerhead 102 and the interior top wall of chamber 100 is approximately11 mm.

It should be understood, of course, that the above dimensions areillustrative and are not intended as limiting. Thus, chamber 100 mayhave any dimensions that permit the desired flow of cleaning gas fromaperture 108 through chamber 100.

FIGS. 3A, 3B, and 3C are side views of chamber 100 showing the flowpatterns in chamber 100 at 0.7 Torr, where the cleaning gas is flowingthrough aperture 108 at 10 standard cubic centimeters per minute (sccm),30 sccm, and 50 sccm, respectively, and no gas is being pumped intochamber 100 via showerhead 102. FIGS. 3A, 3B, and 3C were modeled inFluent UNS version 4.3 from Fluent Inc., located in Lebanon, N. H.,using a two dimensional model of chamber 100 where showerhead 102 andchuck 106 were both sized for a 200 mm wafer, and showerhead 102 andwalls of chamber 100 were assumed to be 50° C. and chuck 106 is at 0° C.The face plate 104 of showerhead 102 has 8407 holes of 0.06 inches indiameter and was treated as a porous media with a permeability of1.75E-8 m². The cleaning gas was assumed to be Oxygen O₂ with a thermalconductivity K of 0.024 w/m-K and a viscosity μ of 1.79E-5 kg/m-s.

As can be seen in FIGS. 3A, 3B, and 3C, the cleaning gas leaves aperture108 at a fairly high velocity, e.g., 4 to 21 meters per second, andimpinges on face plate 108. Most of the gas is deflected by face plate108 and flows radially outward in chamber 100. A small portion of thegas, however, flows through face plate 104, circulates within showerhead102, and flows back out of face plate 104. The flow patterns at thedifferent flow rates, i.e., 10 sccm 30 sccm and 50 sccm are all similarexcept for the recirculation that forms around aperture 108 at higherflow rates. Of course if chuck 106 had more than one aperture providingcleaning gas to chamber 100, the flow pattern will vary from what isshown in FIGS. 3A, 3B, and 3C.

FIGS. 4A, 4B, and 4C are side views of chamber 100 showing the flowpatterns in chamber 100 at 1.0 Torr, where the cleaning gas is flowingthrough aperture 108 at 10 standard cubic centimeters per minute (sccm),30 sccm, and 50 sccm, respectively. The flow patterns shown in FIGS. 4A,4B, and 4C were generated in the same manner as that described inreference to FIGS. 3A, 3B, and 3C, except that the pressure of chamber100 is increased to 1.0 Torr. As can be seen by comparing FIGS. 3A, 3B,and 3C with FIGS. 4A, 4B, and 4C, changing the pressure in chamber 100from 0.7 Torr to 1.0 Torr has no apparent effect on the flow patterns.

Pressure affects the volume within chamber 100 that becomes a plasmaduring application of the RF power. A high pressure constrains theplasma to the area near aperture 108, and a low pressure permits thevolume of the plasma to expand. FIG. 5 is a side view of chamber 100showing the pressure distribution within chamber 100 for the 1.0 Torr,10 sccm flow case, i.e., the flow pattern shown in FIG. 4A. The pressuredistribution in chamber 100 is indicated by dotted isobars. As can beseen, there is a relatively constant pressure distribution throughoutchamber 100, with a high pressure region near aperture 108 and a lowpressure region near annular pumping port 110. However, the highpressure region near aperture 108 is only 0.6 mTorr, which is smallcompared to the total pressure of 1.0 Torr within chamber 100. Thus, thepressure distribution caused by the cleaning gas injection from aperture108 will have little consequence on the volume of the plasma or thestructural integrity of chamber 100. Nevertheless, the presence of thepressure distribution shown in FIG. 5 indicates that the gas will flowfrom the high pressure region to the low pressure region within chamber100.

The in situ cleaning process for chamber 100 is the following. The gassources 114 and 118 are isolated from chamber 100 by closing valves 116and 122, respectively. Vacuum pump 112 then pumps remaining gas out ofchamber 100 via annular pumping port 110, until chamber 100 is at itsbase pressure, e.g., 10 mTorr. The substrate or substrates are removedfrom chamber 100.

Valve 123 opens to permit cleaning gas source 120 to fill chamber 100with a cleaning gas, such as Oxygen O₂, via aperture 108 while vacuumpump 112 continues to pump gas out of chamber 100. Because the cleaninggas is injected into chamber 100 from aperture 108, which is directlybelow face plate 104,, some of the cleaning gas passes through faceplate 104 and into showerhead 102. Cleaning gas source 120 supplies thecleaning gas faster than vacuum pump 112 can drain the gas out ofchamber 100, until a desired pressure is achieved within chamber 100,such as 0.5 to 3.0 Torr. The pressure within chamber 100 is thenstabilized by appropriately regulating the rate that the cleaning gas issupplied to chamber 100 from gas supply 120 via valve 123, and the rateat which the gas is pumped out of chamber 100 by vacuum pump 112 viaannular pumping port 110. Multiple pressures may be used, for example500 mTorr and 1 Torr, which permits different areas of the chamber to becleaned. As described in reference to FIG. 5, changes in pressure willalter the focus of plasma: a high pressure constrains the plasma betweenchuck 106 and showerhead 102, while a low pressure permits the plasma toexpand throughout chamber 100.

Once the pressure conditions are stabilized within chamber 100, the RFpower source 124 supplies RF power to chuck 106 while the cleaning gascontinues to flow into chamber 100 through aperture 108. The RF powersource 124 during cleaning generates 100 to 1000 watts at a frequency of13.56 MHz, which produces an electromagnetic field between showerhead102 and chuck 106. Typically, during cleaning, 300 watts is generated byRF power source 124 in a chamber with the dimensions as disclosed inreference to FIG. 2. The wattage of RF power source 124 may vary,however, depending on the dimension of chamber 100 and the pressuresbeing used. The electromagnetic field forms a plasma of the cleaninggas. Thus, where Oxygen (O₂) is used, a plasma gas containing Oxygenions is generated. Vacuum pump 112 pumps reactant gases out of chamber100 through annular pumping port 110 such that a constant pressure and astable plasma is maintained within chamber 100.

The Oxygen ions chemically react with the contaminants on the interiorsurfaces of chamber 100 to form gaseous by-product, i.e., vapor, andparticles of the contaminant that are pumped out of chamber 100 viaannular pumping port 110 and vacuum pump 112.

Because the cleaning gas is injected into chamber 100 from aperture 108,the cleaning gas interacts with the RF electromagnetic field betweenshowerhead 102 and chuck 106 to form ions before passing through faceplate 104. Thus, the cleaning Oxygen ions are circulated withinshowerhead 102 to react with any contaminants within showerhead 102 toform vapor and particles. The vapor and particles then flow out throughface plate 104 and out of chamber 100 via annular pumping port 110.

After cleaning chamber 100 at one pressure, if desired, a secondpressure may be used. Thus, the rate of flow of the cleaning gas and therate of pumping out chamber 100 are altered until the desired secondpressure is obtained. The cleaning process then continues at the secondpressure. By using multiple pressures, different areas of chamber 100are cleaned. A high pressure, e.g., 1 Torr, is used to effectively cleanthe face plate 104, the surface of chuck 106, and advantageously theinterior of showerhead 102, while a lower pressure, e.g., 500 mTorr, isused to clean the remainder of chamber 100.

After chamber 100 has been cleaned by the reactant gas, e.g., afterapproximately 5 to 60 minutes, RF power source 124 turns off the RFpower to chuck 106 and valve 123 closes to stop the flow of cleaning gasfrom cleaning gas source 120. Valve 116 opens to permit a purging gasfrom gas source 114 to be introduced into chamber 100 through showerhead102 while vacuum pump 112 continues to pump the gas out of chamber 100through annular pumping port 110. Valve 116 is turned off to shut offthe flow of purging gas and chamber 100 is brought down to its basepressure, below 10 mTorr, by vacuum pump 112. The desired gases are thenintroduced into chamber 100 via showerhead 102 and the processing ofsubstrates is resumed.

Although the present invention has been described in considerable detailwith reference to certain versions thereof, other versions are possible.For example, the present invention may be embodied in a chamber with aplurality of chucks and showerheads and/or in a chamber that performs atype of processing other than parylene deposition. The particulargaseous cleaning agent may also be varied according to the desiredapplication. A processing chamber in accordance with an embodiment ofthe present invention may use a gaseous cleaning agent that does notform a plasma. Further, the RF power may be applied in differentmanners, such as by a coil located between aperture 108 and face plate104. Therefore, the spirit and scope of the appended claims should notbe limited to the description of the versions depicted in the figures.

What is claimed is:
 1. A method of cleaning a processing chamber, saidmethod comprising: injecting a gaseous cleaning agent into saidprocessing chamber through at least one aperture positioned below ashowerhead having a porous face plate; causing a portion of said gaseouscleaning agent to flow through said face plate and circulate within saidshowerhead, said portion of said gaseous cleaning agent flowing backthrough said face plate; and pumping said gaseous cleaning agent out ofsaid processing chamber while said gaseous cleaning agent is injectedinto said processing chamber.
 2. The method of claim 1, furthercomprising applying a power source to said processing chamber to form anionizing plasma from said gaseous cleaning agent, wherein said portionof said gaseous cleaning agent that flows through said face platecomprises ions.
 3. The method of claim 1, wherein said power source isapplied between said showerhead and a chuck having said at least oneaperture.
 4. The method of claim 2, wherein said power source is a radiofrequency power source.
 5. The method of claim 1, further comprising:pumping gas remaining within said processing chamber out of saidprocessing chamber to bring said processing chamber to a base pressureprior to injecting said gaseous cleaning agent into said processingchamber; discontinuing the injection of said gaseous cleaning agent intosaid processing chamber; and removing the remaining gaseous cleaningagent from said processing chamber.
 6. The method of claim 5, whereinremoving remaining gaseous cleaning agent from said processing chambercomprises: injecting a purging gas into said processing chamber whilepumping said remaining gaseous cleaning agent and said purging gas outof said processing chamber; discontinuing the injection of said purginggas into said processing chamber; and pumping the remaining gaseouscleaning agent and the remaining purging gas out of said processingchamber to bring said processing chamber to said base pressure.
 7. Themethod of claim 6, wherein said purging gas is injected into saidprocessing chamber from said showerhead.
 8. The method of claim 1,wherein said gaseous cleaning agent comprises Oxygen.